Unix scripts: how to sum numbers up

February 25th, 2009 | Basic stuff, Scripts, Unix

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If you're ever thought of summing up more than two numbers in shell script, perhaps this basic post will be a good start for your Unix scripting experiments.

Basic construction for summing up in shell scripts

In my Basic arithmetic operations in Unix shell post last year, I've shown you how to sum up two numbers:

SUM=$(($NUMBER1 + $NUMBER2)

using the same approach, it's possible to calculate sums of as many numbers as you like, if you use one of the loops available in your shell.

Before we get started, let's create a simple file with numbers we'll work with:

ubuntu$ for i in 1 2 3 4 5 6 7 8 9; do echo $i >> /tmp/nums; done;
ubuntu$ cat /tmp/nums
1
2
3
4
5
6
7
8
9

Using a while loop to sum numbers up in Unix

Here's an example of how you can use a while loop in Unix shell for summing numbers up. Save it as a /tmp/sum.sh script, and don't forget to do chmod a+x /tmp/sum.sh so that you can run it!

#!/bin/sh
#
SUM=0
#
while read NUM
do
        echo "SUM: $SUM";
        SUM=$(($SUM + $NUM));
        echo "+ $NUM: $SUM";
done < /tmp/nums

Here's how the output will look when you run it:

ubuntu$ /tmp/sum.sh
SUM: 0
+ 1: 1
SUM: 1
+ 2: 3
SUM: 3
+ 3: 6
SUM: 6
+ 4: 10
SUM: 10
+ 5: 15
SUM: 15
+ 6: 21
SUM: 21
+ 7: 28
SUM: 28
+ 8: 36
SUM: 36
+ 9: 45

Of course, your data will most probably will be in a less readable form, so you'll have to do a bit of parsing before you get to sum the numbers up, but the loop will be organized in the same way.

That's it for today, enjoy and feel free to ask questions!